Generally, a vehicle exhaust system must perform several demanding and diverse requirements, i.e., attenuating engine noise while porting and reducing emission levels of engine exhaust gas to the atmosphere. In addition, legislative action in combination with typical market driven design concerns have made the need for durable exhaust systems greater than ever before.
Thus, the need for determining exhaust system durability in a cost effective manner has generated demand for a system capable of verifying complete system performance prior to integration with a vehicle. Due to reduced product cycle time, physical testing of system level hardware and durability has been used to validate computer aided engineering (CAD) analysis. However, the methods of determining durability to date have not proven reliable. Thus, physical test fixtures are typically used in an attempt to simulate actual road conditions for measuring system durability.
However, the problem with using physical test fixtures is that reliability of the test results is directly related to the realism with which the input control signals/boundary conditions simulate actual road conditions. While the structural materials of the exhaust system have generally linear responses, other factors such as exhaust hanger isolations, are nonlinear or not well defined but will greatly influence the exhaust system dynamic loads, accelerations, and displacements. As a result, a need exists for a method which can accurately define these control signals and boundary conditions for application to a test fixture.